Surveillance and monitoring systems have been widely employed in many different places to watch over entrance and exit of people and goods thereat to ensure the safety of the general public. Basic apparatuses included in surveillance and monitoring systems are surveillance cameras and monitors electrically connected to a main control unit. Images taken by each surveillance camera are sent to the main control unit and displayed on the monitors for viewing by security guards.
The surveillance cameras may appear in many different forms, and may be generally divided into two types according to the mounting manners: surveillance camera with mounting rack and surveillance camera without mounting rack. The latter may be further divided into a ceiling-mounted and a wall-mounted type. FIG. 1 shows a conventional ceiling-mounted surveillance camera, which includes a base 10, a revolving seat 11, a lens carrier 12, and a lens 13. The lens 13 is fixedly connected to the lens carrier 12, and the lens carrier 12 is locked at two opposite sides to the revolving seat 11 using two clamp screws 14, 15. The revolving seat 11 is screwed to the base 10 and adapted to turn relative to the base 10 within a range without separating from the base 10. The lens 13 must be so positioned that an image of an upright person or object taken by the lens 13 may be displayed on the monitors in a normal state, that is, in the same upright condition. By turning the revolving seat 11 toward a desired direction, the lens 13 may be aimed at an area to be watched over, so that the purpose of surveillance is achieved. A clear hood 16 is connected to a top of the base 10 to protectively enclose the other components therein.
When the above-structured ceiling-mounted surveillance camera is directly mounted to a wall surface, any turning of the revolving seat 11 would result in deformation of the image taken by the lens 13. The deformed image shown on the monitors stops the security guards from quickly and correctly judging the actual state in the surveillance area from the monitors.
Currently, there are many wall-mounted surveillance cameras available in the market. Basically, these wall-mounted cameras must have a lens fixedly aimed at a desired direction without being turned, in order to take images free of any deformation.
FIG. 2 shows a conventional wall-mounted surveillance camera, which has a base 20, a pair of mounting lugs 21 provided in the base 20, a first swing seat 22 angle-adjustably mounted on the mounting lugs 21, a second swing seat 23 angle-adjustably mounted on the first swing seat 22, a lens 24 fixedly mounted on the second swing seat 23, and a hood 25 connected to a top of the base 20. The first and the second swing seat 22, 23 swing in two orthogonal directions, so that the lens 24 may be aimed at any desired direction. However, the base 20 and the hood 25 must be large enough to provide a sufficient space between them for mounting the first and the second swing seat 22, 23 therein. Therefore, the wall-mounted surveillance camera of FIG. 2 has a relatively large volume and is quite noticeable when it is mounted on the wall.